1. Field of the Invention
This invention relates to a semiconductor laser device.
2. Background Art
Blue-violet semiconductor laser devices for the 400 nm wavelength band are promising for application to the next-generation DVD (digital versatile disk). The recording capacity of the next-generation DVD is required to be 15 gigabytes or more on a one-sided, single-layer medium. To this end, the spot size needs to be smaller than in conventional DVDs. Furthermore, for rewriting in this wavelength band, the pulse light output is preferably 200 mW or more.
GaN-based semiconductor laser devices for this purpose needs to provide light output having a kink level of 200 mW (pulse power) or more and to realize a far field pattern (FFP) with less degradation of optical characteristics due to jitter and objective lens shift.
A patent document, JP-A 2002-299765 (Kokai), discloses a semiconductor laser device with a high kink level and a large full width at half maximum of horizontal FFP (Fh). In this document, the insulating film thickness, electrode film thickness, ridge height, and upper cladding layer thickness are configured so that the effective refractive index difference Δn and the ridge width W are located within a particular Δn·W region. However, the teaching of this document is not yet sufficient for meeting the requirements of rewriting applications in the next-generation DVD.